This invention relates specifically to lithium-iodine cells, including lithium anodes and an iodine-poly (2-vinylpyridine) complex cathode or similar cathode material. The operative surface(s) of the lithium anode is coated or otherwise covered with a layer of polymeric organic electron donor material such as poly (2-vinylpyridine), sometimes referred to as P2VP, other materials being known in the art. Briefly, the poly (2-vinylpyridine) or other polymeric organic donor material on the lithium anode may be applied by painting or otherwise depositing a coating of the polymer dissolved in tetrahydrofuran at room temperature. Such an arrangement is more fully described in U.S. Pat. Nos. 3,957,533 and 4,071,662, both to Mead, et al. Alternatively, a self-supporting film of polymeric organic donor material such as poly (2-vinylpyridine) may be placed over the operative anode surfaces. Such film is typically extruded. This is more fully described in U.S. Pat. No. 4,182,798 to Skarstad, assigned to the same assignee as this invention. The term "operative surface(s)" refers to those surface areas of the anode which are exposed in the cell to cathode material.
General teachings concerning cathode materials for lithium iodine cells may be found in U.S. Pat. No. 4,340,651 to Howard, et al. also assigned to the same assignee as this invention. As an example of cathode material, a mixture of iodine and poly (2-vinylpyridine) is heated at an elevated temperature for a time adequate to form a complex composition. The cathode material is then poured into a cell container into which a lithium anode having a coating or film of poly (2-vinylpyridine) thereon (a preferred polymeric organic donor material) has been previously positioned. The cell container is then hermetically sealed. Such cells, in a relatively thin form having a thin planar anode having, most often, two opposed major lateral surfaces, have found particular application in the medical field for heart pacemakers and other medical devices.
Lithium-iodine cells for medical applications have typically been case-positive with cathode material on two sides of a central lithium anode resulting in relatively highly efficient cells. Such cells are so efficient in discharge that they tend to exhaust most of the cell capacity before exhibiting rapid voltage decay at end-of-life (EOL).